Copy guard method and digital broadcast receiving apparatus

ABSTRACT

According to a copy protection method of the present invention, as for a component video signal which is composed of a luminance signal and two color-difference signals, copy inhibition information is superimposed upon a first color-difference signal and information indicating that the copy inhibition information is included in the first color-difference signal is superimposed upon a second color-difference signal. Or copy inhibition information is superimposed upon the luminance signal, a vertical blanking interval, or a horizontal blanking interval. 
     Accordingly, it can be judged whether or not the video is capable of copying, without making the viewers conscious, whereby component video signals can be easily copy protected.

TECHNICAL FIELD

The present invention relates to a method for protecting video dataagainst copying when video data including copy inhibition information isoutputted as a video signal which is composed of a luminance signal andtwo color-difference signals, and a digital broadcast receiver foroutputting a video signal to which this copy protection method has beencarried out.

BACKGROUND ART

As VCRs (Video Cassette Recorders) have been coming into wide use, ithas become possible to easily view video data of recorded televisionbroadcast or contents of software which can be reproduced by the VCR. Inaddition, recently, digital VCRs and recording/reproduction apparatusfor DVDs (Digital Video Discs) have been progressed, wherebyhigh-quality video data can be recorded and reproduced. Since thehigh-quality video data can be easily recorded/reproduced because of therecent progress in the VCRs and the DVD recording/reproductionapparatus, the security of copyrights on video data which are recordedon the digital VCRs or DVDs has become important. Therefore, variousmethods for preventing unauthorized copying have been conventionallycarried out.

For example as for analog video signals, there is a method by whichcopying is protected with utilizing a difference in AGC (Auto GainControl) methods between the VCR and the TV, or a difference incharacteristics of APC (Auto Phase Control).

However, in the conventional copy protection method, only a carriersignal which is obtained by modulation of a color signal can beprotected against copying, while a color-difference signal which is notmodulated cannot be protected against copying. More specifically, for acolor-difference signal which is not modulated as shown in FIG. 15 or acomponent video signal which is composed of primary-color signals, thereis no suitable copy protection method and thus these signals can beeasily copied.

The present invention is made in view of the above-mentioned problemsand has for its object to provide a copy protection method for acomponent signal which is composed of a luminance signal andcolor-difference signals, and a digital broadcast receiver foroutputting the copy-protected component signal.

DISCLOSURE OF THE INVENTION

According to a first aspect of the present invention, there is provideda copy protection method for a component video signal which is composedof a luminance signal and two color-difference signals, comprising stepsof: on a digital broadcast receiver side, superimposing copy inhibitioninformation upon a first one of the two color-difference signals andsuperimposing, upon a second one of the color-difference signals, a copyinhibition information superimposition indication signal indicating thatthe copy inhibition information is superimposed upon the firstcolor-difference signal; and on a recorder side, when the copyinhibition information superimposition indication signal is detected inthe second color-difference signal, analyzing the first color-differencesignal and, when the copy inhibition information is detected in thefirst color-difference signal, carrying out a copy inhibition processwithout performing recording.

Therefore, the component video signal which is composed of a luminancesignal and two color-difference signals can be protected againstunauthorized copying.

According to a second aspect of the present invention, there is provideda digital broadcast receiver comprising: a copy guard detection unit fordetecting whether input video data is copy inhibited or not; and aninformation addition unit for superimposing copy inhibition informationupon a first one of two color-difference signals when the copy guarddetection unit detects that the input video data is copy inhibited andsuperimposing, upon a second one of the color-difference signals, a copyinhibition information superimposition indication signal indicating thatthe copy inhibition information is superimposed upon the firstcolor-difference signal.

Therefore, there can be provided a digital broadcast receiver which,when copy-inhibited video data is received, outputs a component signalincluding two color-difference signals subjected to copy protection ofsuperimposing copy inhibition information upon the firstcolor-difference signal and superimposing a copy inhibition informationindication signal indicating that the copy inhibition information issuperimposed upon the first color-difference signal, upon the secondcolor-difference signal.

According to third aspect of the present invention, in the copyprotection method of the first aspect, the copy inhibition informationis superimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal in field units or in line units.

Therefore, the copy inhibition information can be efficientlysuperimposed upon the color-difference signal of the component signal.

According to a fourth aspect of the present invention, in the digitalbroadcast receiver of the second aspect, when the copy inhibitioninformation is superimposed upon the first color-difference signal andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal, the informationaddition unit performs the superimposition in field units or in lineunits.

Therefore, there can be provided a digital broadcast receiver which canoutputs a component signal including a color-difference signal subjectedto copy protection in field units or in line units.

According to a fifth aspect of the present invention, in the copyprotection method of the first aspect, after the copy inhibitioninformation is superimposed upon the first color-difference signal andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal, in field units,the superimposed color-difference signal of each field and acolor-difference signal of an immediately preceding field are composed.

Therefore, disturbances in video can be reduced when the componentsignal which has been subjected to copy protection in field units isdisplayed on the TV side, and it is possible to prevent the viewers fromrecognizing that the copy inhibition information is superimposed uponthe color-difference signal.

According to a sixth aspect of the present invention, the digitalbroadcast receiver of the second aspect comprises: a color-differencesignal composition unit for, after the copy inhibition information issuperimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal, in field units, composing thesuperimposed color-difference signal of a field and a color-differencesignal of an immediately preceding field.

Therefore, there can be provided a digital broadcast receiver which canreduce disturbances in video when the component signal which has beensubjected to copy protection in field units is displayed on the TV side,and can output a video signal for which the viewers do not recognizethat the copy inhibition information is superimposed upon thecolor-difference signal in field units.

According to a seventh aspect of the present invention, in the copyprotection method of the first aspect, after the copy inhibitioninformation is superimposed upon the first color-difference signal andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal, in line units, thesuperimposed color-difference signal of each line and a color-differencesignal of an immediately preceding line are composed.

Therefore, disturbances in video can be reduced when the componentsignal which has been subjected to copy protection in line units isdisplayed on the TV side, and it is possible to prevent the viewers fromrecognizing that copy inhibition information is superimposed upon thecolor-difference signal in line units.

According to an eighth aspect of the present invention, the digitalbroadcast receiver of the second aspect comprises: a color-differencesignal composition unit for, after the copy inhibition information issuperimposed upon the first color-difference signal in line units andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal, composing thesuperimposed color-difference signal of a line and a color-differencesignal of an immediately preceding line.

Therefore, there can be provided a digital broadcast receiver which canreduced disturbances in video when the component signal subjected tocopy protection in line units is displayed on the TV side, and canoutput a video signal for which the viewers do not recognize that thecopy inhibition information is superimposed upon the color-differencesignal in line units.

According to a ninth aspect of the present invention, in the copyprotection method of any of the first, third, fifth and seventh aspect,when the copy inhibition information is superimposed upon the firstcolor-difference signal and the copy inhibition informationsuperimposition indication signal is superimposed upon the secondcolor-difference signal, they are superimposed at irregular intervals.

Therefore, when the component signal which has been subjected to copyprotection is displayed on the TV side, it is possible to prevent theviewers from recognizing that the copy inhibition information issuperimposed.

According to a tenth aspect of the present invention, the digitalbroadcast receiver of any of the second, fourth, sixth and eighthaspects comprises: an additional signal control unit for, when the copyinhibition information is superimposed upon the first color-differencesignal and the copy inhibition information superimposition indicationsignal is superimposed upon the second color-difference signal,performing control for superimposing the same at irregular intervals.

Therefore, there can be provided a digital broadcast receiver which canoutput a component signal that is not recognized by the viewers when thesignal upon which copy inhibition information has been superimposed atirregular intervals and subjected to copy protection is displayed on theTV side.

According to an eleventh aspect of the present invention, there isprovided a copy protection method for a component video signal which iscomposed of a luminance signal and two color-difference signals,comprising steps of: on a digital broadcast transmitting end, invertinga synchronizing signal included in the luminance signal; on a digitalbroadcast receiving end, when it is detected that the synchronizingsignal is inverted, inverting the synchronizing signal again to obtainthe original signal; and on a recorder end, when it is detected that thesynchronizing signal is inverted, carrying out a copy inhibition processwithout performing recording.

Therefore, when the component signal which has been subjected to copyprotection is outputted on the TV side, it is displayed on the screen asusual, while when the component signal is recorded on the recording end,the recording is not performed.

According to a twelfth aspect of the present invention, there isprovided a digital broadcast receiver comprising: a copy guard detectionunit for detecting whether input video data is copy inhibited or not;and a synchronizing signal inversion unit for, when the copy guarddetection unit detects that the video data is copy inhibited, invertinga synchronizing signal included in a luminance signal which is to beoutputted.

Therefore, there can be provided a digital broadcast receiver which canoutput a luminance signal subjected to copy protection of inverting asynchronizing signal, when copy-inhibited video is inputted.

According to a thirteenth aspect of the present invention, there isprovided a copy protection method for a component video signal which iscomposed of a luminance signal and two color-difference signals,comprising steps of: inverting the luminance signal, and superimposing aluminance signal inversion indication signal indicating that theluminance signal is inverted, upon a vertical blanking interval of oneor both of the color-difference signals; on a TV side, when theluminance signal inversion indication signal is detected in the verticalblanking interval of the color-difference signal, inverting theluminance signal again to obtain the original signal; and on a recorderside, when the luminance signal inversion indication signal is detectedin the vertical blanking interval of the color-difference signal,deleting the luminance signal inversion indication signal and recordingthe inverted luminance signal as it is, or carrying out a copyinhibition process.

Therefore, the inverted luminance signal of the component signal whichhas been subjected to copy protection is recorded as it is, or the copyinhibition process is carried out when the inverted luminance signal isdetected, thereby protecting the inputted video signal againstunauthorized copying.

According to a fourteenth aspect of the prresent invention, there isprovided a digital broadcast receiver comprising: a copy guard detectionunit for detecting whether input video data is copy inhibited or not; aluminance signal inversion unit for inverting a luminance signal whenthe copy guard detection unit detects that the video data is copyinhibited; and an information addition unit for superimposing aluminance signal inversion indication signal indicating that theluminance signal is inverted, upon a vertical blanking interval of acolor-difference signal.

Therefore, there can be provided a digital broadcast receiver which canoutput a component video signal subjected to copy protection ofinverting the luminance signal as well as superimposing a luminancesignal inversion indication signal indicating that the luminance signalis inverted, upon the vertical blanking interval of the color-differencesignal, when copy-inhibited video data is inputted.

According to a fifteenth aspect of the present invention, there isprovided a copy protection method for a component video signal which iscomposed of a luminance signal and two color-difference signals,comprising steps of: inverting the luminance signal, and superimposing aluminance signal inversion indication signal indicating that theluminance signal is inverted, upon a horizontal blanking interval of oneor both of the color-difference signals; on a TV side, when theluminance signal inversion indication signal is detected in thehorizontal blanking interval of the color-difference signal, invertingthe luminance signal again to obtain the original signal; and on arecorder side, when the luminance signal inversion indication signal isdetected in the horizontal blanking interval of the color-differencesignal, deleting the luminance signal inversion indication signal andrecording the inverted luminance signal as it is, or carrying out a copyinhibition process.

Therefore, the inverted luminance signal of the component signal whichhas been subjected to the copy protection is recorded as it is, or acopy inhibition process is carried out when the inverted luminancesignal is detected, thereby protecting the inputted video signal fromunauthorized copying.

According to a sixteenth aspect of the present invention, there isprovided a digital broadcast receiver comprising: a copy guard detectionunit for detecting whether input video data is copy inhibited or not; aluminance signal inversion unit for inverting a luminance signal whenthe copy guard detection unit detects that the video data is copyinhibited; and an information addition unit for superimposing aluminance signal inversion indication signal indicating that theluminance signal is inverted, upon a horizontal blanking interval of acolor-difference signal.

Therefore, there can be provided a digital broadcast receiver which canoutput a component video signal subjected to copy protection ofinverting a luminance signal and superimposing a luminance signalinversion indication signal indicating that the luminance signal isinverted, upon the horizontal blanking interval of the color-differencesignal, when copy-inhibited video data is inputted.

According to a seventeenth aspect of the present invention, there isprovided a copy protection method for a component video signal which iscomposed of a luminance signal and two color-difference signals,comprising steps of: superimposing copy inhibition video whichinterferes with video, upon a start part or an end part of a videoeffective period of a field, and delaying or advancing a start positionof a normal video signal by the superimposed copy inhibition video;superimposing, upon a vertical blanking interval of the luminance signalor one or both of the color-difference signals, a copy inhibition videosuperimposition indication signal indicating that the copy inhibitionvideo is superimposed upon the start part or the end part of the videoeffective period of the field; on a TV side, when the copy inhibitionvideo superimposition indication signal is detected, deleting the copyinhibition video and returning the normal video signal to the videoeffective period of the field; and on a recorder side, when the copyinhibition video superimposition indication signal is detected, deletingthe copy inhibition video superimposition indication signal andrecording the video signal, so that when the video signal is reproduced,the copy inhibition video is displayed on an upper part or a lower partof a monitor screen and the normal video is not displayed.

Therefore, when a copy-inhibited input video signal is copied anddisplayed, the normal video is made not to be displayed, whereby theinputted video signal can be protected against unauthorized copying.

According to an eighteenth aspect of the present invention, there isprovided a digital broadcast receiver comprising: a copy guard detectionunit for detecting whether input video data is copy inhibited or not; acopy inhibition video insertion unit for, when the copy guard detectionunit detects that the video data is copy inhibited, superimposing copyinhibition video which interferes with video, upon a start part or anend part of a video effective period of a field, and delaying oradvancing a start position of a normal video signal by the superimposedcopy inhibition video; and an information addition unit forsuperimposing, upon a vertical blanking interval of a luminance signalor one of both of color-difference signals, a copy inhibition videosuperimposition indication signal indicating that the copy inhibitionvideo is superimposed upon the start part or the end part of the videoeffective period of the field.

Therefore, there can be provided a digital broadcast receiver whichinserts copy inhibition video when it detects that an inputted videosignal is copy inhibited, thereby protecting the inputted video signalagainst unauthorized copying.

According to a nineteenth aspect of the present invention, there isprovided a copy protection method for a component video signal which iscomposed of a luminance signal and two color-difference signals,comprising steps of: superimposing copy inhibition video upon a startpart or an end part of a video effective period of a line, and delayingor advancing a start position of a normal video signal by thesuperimposed copy inhibition video; superimposing, upon a verticalblanking interval of the luminance signal or one or both of thecolor-difference signals, a copy inhibition video superimpositionindication signal indicating that the copy inhibition video issuperimposed upon the start part or the end part of the video effectiveperiod of the line; on a TV side, when the copy inhibition videosuperimposition indication signal is detected, deleting the copyinhibition video and returning the original video signal to the videoeffective period of the line; and on a recorder side, when the copyinhibition video superimposition indication signal is detected, deletingthe copy inhibition video superimposition indication signal andrecording the video signal, so that when the video signal is reproduced,the copy inhibition video is displayed on a left part or a right part ofa monitor screen and the normal video is not displayed.

Therefore, when the inputted copy-inhibited video is copied anddisplayed, the normal video is made not to be displayed, whereby theinputted video signal can be protected against unauthorized copying.

According to a twentieth aspect of the present invention, there isprovided a digital broadcast receiver comprising: a copy guard detectionunit for detecting whether input video data is copy inhibited or not; acopy inhibition video insertion unit for, when the copy guard detectionunit detects that the input video data is copy inhibited, superimposingcopy inhibition video which interferes with video, upon a start part oran end part of a video effective period of a line, and delaying oradvancing a start position of a normal video signal by the superimposedcopy inhibition video; and an information addition unit forsuperimposing the copy inhibition video superimposition indicationsignal upon a vertical blanking period of a luminance signal or one orboth of color-difference signals.

Therefore, there can be provided a digital broadcast receiver whichinserts copy inhibition video when it detects that an inputted videosignal is copy inhibited, thereby protecting the copy-inhibited inputtedvideo signal against unauthorized copying.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a structure of a digital broadcastreceiver for outputting a copy-protected component video signalaccording to a first embodiment.

FIG. 2 is a waveform diagram showing a luminance signal andcolor-difference signals, which are copy protected according to thefirst embodiment.

FIG. 3 is a waveform diagram showing a first color-difference signalaccording to a second embodiment.

FIG. 4 is a diagram illustrating a structure of a digital broadcastreceiver for outputting a copy-protected component video signalaccording to the second embodiment.

FIG. 5 is a diagram illustrating a structure of a digital broadcastreceiver for outputting a copy-protected component video signalaccording to a third embodiment.

FIG. 6 is a waveform diagram showing a normal ternary signal and aninverted ternary signal.

FIG. 7 is a diagram illustrating a structure of a digital broadcastreceiver for outputting a copy-protected component video signalaccording to a fourth embodiment.

FIG. 8 is a waveform diagram showing a luminance signal and acolor-difference signal which are copy protected according to a fifthembodiment.

FIG. 9 is a diagram illustrating a structure of a digital broadcastreceiver for outputting a copy-protected component video signalaccording to the fifth embodiment.

FIG. 10 is a waveform diagram showing a luminance signal includingvertical blanking intervals.

FIG. 11 is a waveform diagram showing a luminance signal which is copyprotected in field units according to a sixth embodiment.

FIG. 12 is a waveform diagram showing a luminance signal includinghorizontal blanking intervals.

FIG. 13 is a waveform diagram showing a luminance signal which is copyprotected in line units according to the sixth embodiment.

FIG. 14 is a diagram illustrating a structure of a digital broadcastreceiver for outputting a copy-protected component video signalaccording to the sixth embodiment.

FIG. 15 is an output diagram showing a conventional component videosignal.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a copy protection method and a digital broadcast receiveraccording to embodiments of the present invention will be described withreference to figures. According to this invention, a video signal to becopy guarded and a video signal outputted by the digital broadcastreceiver are so-called component video signals each being composed ofone luminance signal and two color-difference signals, such as Y/U/V,Y/Pb/Pr, and Y/Cb/Cr. Hereinafter, one combination, i.e., either acombinations of color-difference signals U, Pb and Cb or a combinationof color-difference signals V, Pr and Cr is referred to as a firstcolor-difference signal, and the other is referred to as a secondcolor-difference signal.

[Embodiment 1]

A copy protection method and a digital broadcast receiver according to afirst embodiment of the present invention will be described withreference to FIGS. 1 and 2.

Initially, the copy protection method of the first embodiment isdescribed with reference to FIG. 2.

FIG. 2 is a waveform diagram showing a luminance signal andcolor-difference signals which are copy protected in the firstembodiment. In FIG. 2, reference numeral 4 denotes a synchronizingsignal included in a luminance signal in a component video signal.Numeral 5 denotes copy inhibition information which is superimposed upona first color-difference signal, with a normal video color-differencesignal being removed from the first color-difference signal. Numeral 6denotes a copy inhibition information superimposition indication signal,which is superimposed upon a horizontal blanking interval part of asecond color-difference signal, indicating that copy inhibitioninformation is superimposed upon the other color-difference signal,i.e., the first color-difference signal.

FIG. 1 is a block diagram illustrating a digital broadcast receiveraccording to the first embodiment.

In FIG. 1, reference numeral 1 denotes a copy guard detection unit fordetecting copy-guarded information from input video data or systeminformation which is transmitted together with video data. Numeral 2denotes an information addition unit for copy protecting a componentvideo signal to be outputted, when an inputted video signal is copyinhibited. Numeral 3 denotes an MPEG decoder for outputting the inputvideo data from the copy guard detection unit 1 as a component signalwhich is composed of a luminance signal and two color-differencesignals.

When the copy inhibition video data is outputted as a component videosignal which is composed of a luminance signal and two color-differencesignals, a color-difference signal of normal video is removed from thefirst color-difference signal and copy inhibition information 5 issuperimposed thereon as shown in FIG. 2. Further, as for the secondcolor-difference signal, a copy inhibition information superimpositionindication signal 6 indicating that copy inhibition information issuperimposed upon the first color-difference signal is inserted in thehorizontal blanking interval, in synchronization with the synchronizingsignal 4. Here, the copy inhibition information superimpositionindication signal 6 is not restrictively superimposed upon thehorizontal blanking interval but may be superimposed upon the verticalblanking interval or the video period not in synchronization with thesynchronizing signal 4.

On the side of a recorder which records a component video signal, thecolor-difference signals of the inputted component video signal aremonitored and, when the copy inhibition information superimpositionindication signal 6 indicating that the copy inhibition information issuperimposed upon the first color-difference signal is detected from thesecond color-difference signal, the first color-difference signal isanalyzed. Then, when the information which is superimposed upon thefirst color-difference signal is the copy inhibition information 5,recording of the component video signal is not performed but the copyinhibition process is performed, thereby preventing unauthorizedcopying.

Even when this copy-protected component video signal is outputted on theTV side as it is, since the copy inhibition information 5 issuperimposed only upon the color-difference signal, the viewers hardlyrecognize it.

Next, with reference to FIG. 1, the operation of the digital broadcastreceiver for outputting a copy-protected video signal according to thefirst embodiment will be described.

As shown in FIG. 1, video data is initially inputted to the copy guarddetection unit 1. Then, in the copy guard detection unit 1, it is judgedwhether the video data is copy inhibited or not, on the basis of theinput video data or system information transmitted together with videodata and the like. Next, the input video data is transferred to the MPEGdecoder 3, and outputted as a component signal which is composed of aluminance signal, a first color-difference signal, and a secondcolor-difference signal.

When the input video data is judged by the copy guard detection unit 1that it is copy inhibited, the copy guard detection unit 1 outputs asignal for copy protection to the information addition unit 2. Theinformation addition unit 2 which has received the signal superimposesthe copy inhibition information 5 upon the first color-differencesignal, and superimposes the copy inhibition information superimpositionindication signal 6 indicating that the copy inhibition information 5 issuperimposed upon the first color-difference signal, upon the secondcolor-difference signal.

In the case where the copy inhibition information 5 is superimposed uponthe first color-difference signal and further the copy inhibitioninformation superimposition indication signal 6 is superimposed upon thesecond color-difference signal by the information addition unit 2, theycan be superimposed in field units or line units. In addition,information other than the copy inhibition information can besuperimposed upon the first color-difference signal, and a signalindicating that the information for the video signal is superimposedupon the first color-difference signal can be superimposed upon theother signal, i.e., the second color-difference signal.

For example, when information is superimposed upon the component videosignal in field units, more information can be superimposed in the casewhere information other than the copy inhibition information issuperimposed upon the color-difference signal. On the other hand, wheninformation is superimposed in line units, it is possible to prevent theviewers from recognizing that the information is superimposed upon thecolor-difference signal when the video is outputted on the TV side.

As described above, according to the copy protection method and thedigital broadcast receiver of this first embodiment, the copy inhibitioninformation 5 is superimposed upon a color-difference signal of acomponent video signal, whereby the copy inhibition information can beadded to the component video signal with the viewers hardly recognizingit even when the video signal is outputted on the screen. Further, thecopy inhibition information superimposition indication signal 6indicating that the copy inhibition information is superimposed upon onecolor-difference signal is superimposed upon the other color-differencesignal, whereby the copy inhibition information 5 can be recognizedaccurately when the copy inhibition information is superimposed upon anyof color-difference signals.

[Embodiment 2]

A copy protection method and a digital broadcast receiver according to asecond embodiment of the present invention will be described withreference to FIGS. 3 and 4.

FIG. 3 shows a waveform diagram of a first color-difference signalaccording to the second embodiment. In FIG. 3, numeral 7 denotes a firstcolor-difference signal of a previous field. Numeral 8 denotes a signalwhich is obtained by composing the first color-difference signal of theprevious field and copy inhibition information 5.

FIG. 4 is a block diagram illustrating a digital broadcast receiveraccording to the second embodiment. In FIG. 4, numeral 9 denotes acolor-difference signal composition unit for holding a firstcolor-difference signal 7 of a previous field of the firstcolor-difference signal upon which copy inhibition information 5 hasbeen superimposed by the information addition unit 2, and composing thesignal 7 and the first color-difference signal upon which the copyinhibition information 5 has been superimposed. Other components are thesame as those in the digital broadcast receiver of the first embodiment.

Initially, the copy protection method of the second embodiment will bedescribed with reference to FIG. 3.

In the first embodiment, the copy inhibition information 5 issuperimposed by removing the color-difference signal of actual video.However, in the first embodiment, since the color-difference signal isremoved, the viewers may recognize that the copy inhibition informationis superimposed upon the color-difference signal. In this secondembodiment, as shown in FIG. 3, the first color-difference signal uponwhich the copy inhibition information 5 outputted from the informationaddition unit 2 has been superimposed and the first color-differencesignal 7 of the immediately preceding field are composed by thecolor-difference signal composition unit 9, thereby creating the firstcolor-difference signal 8 in which the first color-difference signal ofthe previous field and the copy inhibition information 5 are composed.Accordingly, even when a component video signal which has been subjectedto the above-mentioned copy protection is outputted on the TV side as itis, it is possible to further prevent the viewers from recognizing thatthe copy inhibition information 5 is superimposed upon thecolor-difference signal of the video signal.

In addition, on the side of a recorder which records the component videosignal, when the first color-difference signal 8 is analyzed, only thecopy inhibition information 5 is extracted from the firstcolor-difference signal 8 as a composite signal by using the firstcolor-difference signal 7 of the previous field. Since the signal iscomposed using the first color-difference signal 7 of the previousfield, this extraction of the copy inhibition information 5 can beeasily performed.

Next, the operation of the digital broadcast receiver for outputting acopy-protected video signal according to the second embodiment will bedescribed with reference to FIG. 4.

Initially, when the copy guard detection unit 1 detects that input videodata is copy inhibited, the copy guard detection unit 1 transmits asignal for copy protection to the information addition unit 2 and thecolor-difference signal composition unit 9. Then, the informationaddition unit 2 superimposes the copy inhibition information 5 upon thefirst color-difference signal outputted from the MPEG decoder 3,superimposes the copy inhibition information superimposition indicationsignal 6 indicating that the copy inhibition information 5 issuperimposed upon the first color-difference signal, upon the secondcolor-difference signal, and thereafter transmits these color-differencesignals to the color-difference signal composition unit 9. Thecolor-difference signal composition unit 9 holds the firstcolor-difference signal 7 of the previous field and, when it receivesthe signal for copy protection from the copy guard detection unit 1,composes the first color-difference signal including the copy inhibitioninformation 5 and the held first color-difference signal 7 of theprevious field.

The composition of the first color-difference signal 8 in thecolor-difference signal composition unit 9 may be performed in fieldunits or in line units. For example, when the copy inhibitioninformation 5 is inserted into the first color-difference signal in lineunits, a first color-difference signal of a previous line is held andcomposed. Since the composition of the first color-difference signal 8in line units and the extraction of the copy inhibition information 5from the signal 8 is performed using the first color-difference signalof the previous line, it can be easily performed.

Here, the first color-difference signal of a previous field or aprevious line is composed only with the first color-difference signalupon which the copy inhibition information 5 has been superimposed.However, it is more effective when the color-difference signal of aprevious field or a previous line is composed also with the secondcolor-difference signal upon which the copy inhibition informationsuperimposition indication signal 6 is superimposed, like in the case ofthe first color-difference signal.

As described above, according to the copy protection method and thedigital broadcast receiver of this second embodiment, upon the firstcolor-difference signal, the composite signal 8 in which the copyinhibition information 5 and the first color-difference signal 7 of theimmediately preceding field are composed is superimposed, whereby theviewers more hardly recognize that the copy inhibition information 5 issuperimposed upon the color-difference signal. Further, the composedsignal 8 is created by the composition of the color-difference signal 7of the immediately preceding field, whereby the creation of the composedsignal 8 or the extraction of the copy inhibition information 5 from thesignal 8 can be easily performed.

Like in the first embodiment, the information to be superimposed uponthe first color-difference signal can be information other than the copyinhibition information and further the signal to be superimposed uponthe second color-difference signal can be a signal which indicates thatinformation is superimposed upon the first color-difference signal.

[Embodiment 3]

A copy protection method and a digital broadcast receiver according to athird embodiment of the present invention will be described withreference to FIG. 5.

FIG. 5 is a block diagram illustrating a digital broadcast receiveraccording to the third embodiment. In FIG. 5, numeral 10 denotes aninformation addition control unit for controlling a cycle in which acopy protection process is carried out. Other components are the same asthose in the digital broadcast receiver according to the firstembodiment.

Initially, the copy protection method of the third embodiment isdescribed.

When the copy inhibition information 5 is superimposed upon the firstcolor-difference signal and the copy inhibition informationsuperimposition indication signal 6 indicating that the copy inhibitioninformation is superimposed upon the first color-difference signal issuperimposed upon the second color-difference signal at regularintervals as described above, it is easier to be recognized by theviewers. Accordingly, in this third embodiment, these signals aresuperimposed at irregular intervals. When these signals are superimposedirregularly, it is possible to further prevent the viewers fromrecognizing that these signals are superimposed as compared to the casewhere these signals are superimposed at regular intervals.

Next, the operation of the digital broadcast receiver for outputtingcopy-protected video signals according to the third embodiment will bedescribed with reference to FIG. 5.

Initially, when the copy guard detection unit 1 detects that input videodata is copy inhibited, the copy guard detection unit 1 transmits asignal to the information addition control unit 10 so as to copy protecta component video signal which is outputted from the MPEG decoder 3.When the information addition control unit 10 receives this signal, ittransmits the signal for copy protection to the information additionunit 2 at irregular intervals. The information addition unit 2 carriesout a copy protection process for a color-difference signal which isoutputted from the MPEG decoder 3, at a timing when it receives thesignal for the copy protection. Thereby, the above-mentioned copyprotection process can be superimposed upon the color-difference signalirregularly.

In a case where the information addition control unit 10 is added to thedigital broadcast receiver as described in the second embodiment, whenthe information addition control unit 10 receives the signal for thecopy protection from the copy guard detection unit 1, it transmits thesignal to the information addition unit 2 and the color-differencesignal composition unit 9 at irregular intervals. Then, in theinformation addition unit 2 and the color-difference signal compositionunit 9, the above-mentioned copy protection process is carried out forthe color-difference signal at irregular intervals.

As described above, according to the copy protection method and thedigital broadcast receiver of this third embodiment, the copy inhibitioninformation 5 is superimposed upon the color-difference signal atirregular intervals, whereby it becomes harder for the viewer torecognize that the information is superimposed, as compared to the firstand second embodiments. Like in the first and second embodiment, theinformation to be superimposed upon the first color-difference signalcan be information other than the copy inhibition information andfurther the signal to be superimposed upon the second color-differencesignal can be a signal indicating that information is superimposed uponthe first color-difference signal.

[Embodiment 4]

A copy protection method and a digital broadcast receiver according to afourth embodiment of the present invention will be described withreference to FIGS. 6 and 7.

FIG. 6 is a diagram showing a normal ternary signal and an invertedternary signal. Numeral 11 denotes a normal ternary signal and numeral12 denotes an inverted ternary signal.

FIG. 7 is a block diagram illustrating a digital broadcast receiveraccording to the fourth embodiment. In FIG. 7, numeral 1 denotes a copyguard detection unit. Numeral 3 denotes an MPEG decoder. Numeral 13denotes a synchronizing signal inversion unit for outputting a luminancesignal having an inverted synchronizing signal.

Initially, the copy protection method according to the fourth embodimentis described with reference to FIG. 6.

When a component video signal is outputted, a ternary signal 11 isusually used as a synchronizing signal included in the luminance signalof the component video signal. In the copy protection method accordingto this fourth embodiment, this synchronizing signal as the ternarysignal is inverted and when the inverted synchronizing signal 12 isdetected on the recorder side, recording of the component video signalis not performed but the copy inhibition process is carried out, therebypreventing unauthorized copying.

Further, in the case where the above-mentioned copy-protected componentvideo signal is outputted as it is on the TV side, when thesynchronizing signal 12 as the inverted ternary signal is detected, thissynchronizing signal 12 is inverted again to restore the signal to theoriginal normal ternary signal, and then the normal ternary signal isoutputted. Accordingly, it becomes possible to prevent the viewer fromrecognizing that the video signal is copy protected.

Next, the operation of the digital broadcast receiver for outputtingcopy-protected video signals according to the fourth embodiment will bedescribed with reference to FIG. 7.

Initially, when the copy guard detection unit 1 detects that input videodata is copy inhibited, the copy guard detection unit 1 transmits asignal to the synchronizing signal inversion unit 13 so as to invert asynchronizing signal. When the synchronizing signal inversion unit 13receives this signal, it inverts the synchronizing signal included in aluminance signal which is outputted from the MPEG decoder 3, and outputsa luminance signal including an inverted synchronizing signal 12 asshown in FIG. 6.

As described above, according to the copy protection method and thedigital broadcast receiver of this fourth embodiment, no copy inhibitioninformation is superimposed upon the color-difference signal and theluminance information themselves. Therefore, the copy protection processcan be carried out without being recognized by the viewers at all on thedisplay screen.

[Embodiment 5]

A copy protection method and a digital broadcast receiver according to afifth embodiment of the present invention will be described withreference to FIGS. 8 and 9.

FIG. 8 is a waveform diagram showing a luminance signal and acolor-difference signal which are copy protected according to the fifthembodiment. In FIG. 8, numeral 14 denotes a luminance signal inversionindication signal which indicates that a luminance signal is inverted.

FIG. 9 is a block diagram illustrating a digital broadcast receiveraccording to the fifth embodiment. In FIG. 9, numeral 1 denotes a copyguard detection unit. Numeral 3 denotes an MPEG decoder. Numeral 15denotes a luminance signal inversion unit for inverting a luminancesignal. Numeral 16 denotes an information addition unit forsuperimposing a luminance signal inversion indication signal whichindicates that a luminance signal is inverted, upon a vertical blankinginterval or a horizontal blanking interval of one or both ofcolor-difference signals.

Initially, the copy protection method according to the fifth embodimentwill be described with reference to FIG. 8.

In the fourth embodiment, the synchronizing signal included in theluminance signal is inverted, thereby copy protecting the video data.However, in this fifth embodiment, as shown in FIG. 8, the luminancesignal is inverted and simultaneously a luminance signal inversionindication signal 14 indicating that the luminance signal is inverted issuperimposed upon a horizontal blanking interval of one or both ofcolor-difference signals. For example, as shown in FIG. 8, the luminancesignal inversion indication signal 14 is inserted in the horizontalblanking interval of the color-difference signal in synchronization withthe synchronizing signal included in the luminance signal.

On the recorder side, when the luminance signal inversion indicationsignal 14 indicating that the luminance signal is inverted is detectedin the horizontal blanking interval of the color-difference signal, theluminance signal inversion indication signal 14 is deleted, and thecomponent video signal including the inverted luminance signal isrecorded as it is or subjected to the copy inhibition process, therebypreventing unauthorized copying. When this copy-protected video signalis recorded and reproduced, since the luminance signal inversionindication signal 14 is deleted, the video signal is outputted with theluminance signal being inverted on the display screen.

Further, in the case where the above-mentioned copy-protected componentvideo signal is outputted on the TV side, when the luminance signalinversion indication signal 14 indicating that the luminance signal isinverted is detected in the horizontal blanking interval of thecolor-difference signal, the luminance signal is inverted to berestored, and thereafter this restored signal is outputted. Thereby, itbecomes possible to prevent the viewers from recognizing that the videosignal is copy protected.

Further, the synchronizing signal may be also inverted when theluminance signal is inverted. In this case, when the video signal isoutputted on the TV side, the synchronizing signal is also inverted tobe restored, together with the luminance signal.

Here, the luminance signal inversion indication signal 14 indicatingthat the luminance signal is inverted is inserted in the horizontalblanking interval of the color-difference signal, while this signal maybe inserted in the vertical blanking interval.

Next, the operation of the digital broadcast receiver for outputtingcopy-protected video signals according to the fifth embodiment will bedescribed with reference to FIG. 9.

Initially, when the copy guard detection unit 1 detects that input videodata is copy inhibited, the copy guard detection unit 1 transmits asignal for copy protection to the luminance signal inversion unit 15 andthe information addition unit 16. When receiving this signal, theluminance signal inversion unit 15 inverts the luminance signal, and theinformation addition unit 16 superimposes the luminance signal inversionindication signal 14 indicating that the luminance signal is inverted,upon the vertical blanking interval or the horizontal blanking intervalof one or both of the color-difference signals.

As described above, according to the copy protection method and thedigital broadcast receiver of the fifth embodiment, when the componentvideo signal to be recorded is copy inhibited, the luminance signal isinverted and the luminance signal inversion indication signal 14indicating that the luminance signal is inverted is superimposed uponone of the color-difference signals. Therefore, at the normal screendisplay, when the luminance signal inversion indication signal 14 isdetected, the inverted luminance signal is restored and then outputted,whereby the video signal can be displayed on the screen without beingrecognized by the viewers at all that the copy inhibition information issuperimposed. On the other hand, when copied video is reproduced, videohaving inverted luminance is displayed on the screen, whereby it can bejudged to be copied video.

[Embodiment 6]

A copy protection method and a digital broadcast receiver according to asixth embodiment of the present invention will be described withreference to FIGS. 10, 11, 12, 13 and 14.

FIG. 10 shows a luminance signal including a vertical blanking interval.FIG. 11 shows a luminance signal which is copy protected in field unitsaccording to the sixth embodiment. In addition, FIG. 12 shows aluminance signal including a horizontal blanking interval. FIG. 13 showsa luminance signal which is copy protected in line units according tothe sixth embodiment.

In FIG. 11, numeral 17 denotes a copy inhibition video. Numeral 18denotes a copy inhibition video superimposition indication signal whichindicates that the copy inhibition video 17 is superimposed.

In FIG. 14, numeral 1 denotes a copy guard detection circuit. Numeral 3denotes an MPEG decoder. Numeral 19 denotes an information addition unitfor superimposing the copy inhibition video superimposition indicationsignal 18 indicating that the copy inhibition video 17 is superimposed,upon a luminance signal or one or both of color-difference signals.Numeral 20 denotes a copy inhibition video insertion unit for insertingthe copy inhibition video into the luminance signal and thecolor-difference signal.

Initially, the copy protection method according to the sixth embodimentwill be described with reference to FIGS. 10, 11, 12 and 13.

A video signal includes a vertical blanking interval and a horizontalblanking interval and these parts are not displayed on the displayscreen.

As shown in FIG. 10, since the vertical blanking interval usuallyincludes no data, video data can be delayed or advanced by a periodimmediately after the end of an equalization period until video startsor a period after video ends until an equalization period starts.Therefore, the copy inhibition video 17 of this period can besuperimposed upon the luminance signal. Then, as shown in FIG. 11, thecopy inhibition video 17 is superimposed upon a start part or an endpart of a video effective period of a field of the luminance signal, andthe start position of normal video data is delayed or advanced towardthe end part or the start part of the field by the superimposed copyinhibition video 17. When this copy inhibition video 17 is superimposed,the copy inhibition video superimposition indication signal 18indicating that the copy inhibition video 17 is superimposed upon thestart part or the end part of the video effective period of the field issimultaneously superimposed upon the vertical blanking interval of theluminance signal or one or both of the color-difference signal. Forexample, as shown in FIG. 11, the copy inhibition video superimpositionindication signal 18 is inserted in the vertical blanking interval ofthe luminance signal.

On the recorder side, when the copy inhibition video superimpositionindication signal 18 indicating that the copy inhibition video 17 issuperimposed upon the start part or the end part of the video effectiveperiod of the field is detected, the video signal is recorded withdeleting the copy inhibition video superimposition indication signal 18or the copy inhibition process is carried out, thereby preventingunauthorized copying. When the video signal which has been subjected tothe copy protection is recorded and reproduced, since the copyinhibition video superimposition indication signal 18 indicating thatthe copy inhibition video 17 is inserted into the start part or the endpart of the video effective period of the field is deleted, the copyinhibition video 17 is displayed on the TV side on the upper part or thelower part of the display screen.

Further, in the case where the component video signal which has beensubjected to the above-mentioned copy protection is outputted on the TVside, when the copy inhibition video superimposed indication signal 18indicating that the copy inhibition video 17 is superimposed isdetected, the copy inhibition video 17 is deleted, and then the normalvideo part is restored to the video effective period of the field,thereby obtaining the signal as shown in FIG. 10. Accordingly, it ispossible to prevent the viewers from recognizing that the video signalis copy protected.

In the above descriptions, the method for copy protecting a componentvideo signal has been explained, by which the copy inhibition video 17is superimposed upon a start part or an end part of a video effectiveperiod of a field of the luminance signal. However, as shown in FIG. 12,since the horizontal blanking interval also has parts including novideo, i.e., a front porch and a back porch, the copy inhibition video17 can be superimposed upon a start part or an end part of a line asshown in FIG. 13. In this case, the copy inhibition video 17 issuperimposed thereupon by a period of a front porch or a back porch, andthe copy inhibition video superimposition instruction signal 18indicating that the copy inhibition video 17 is superimposed upon thestart part or the end part of the video effective period of the line issuperimposed upon the vertical blanking interval of the luminance signalor one or both of the color-difference signals. Thereby, unauthorizedcopying can be prevented as in the case where the copy inhibition video17 is superimposed upon the start part or the end part of the videoeffective period of the field. When this copy-protected video signal isrecorded and reproduced, the copy inhibition video 17 is displayed onthe TV side on the left part or the right part of the display screen.

The copy inhibition video superimposition indication signal 18 may beinserted in the horizontal blanking interval, not in the verticalblanking interval.

Next, the digital broadcast receiver for outputting copy-protected videosignals according to the sixth embodiment will be described withreference to FIG. 14.

Initially, when the copy guard detection unit 1 detects that input videodata is copy inhibited, the copy guard detection unit 1 transmits asignal for copy protection to the information addition unit 19 and thecopy inhibition video insertion unit 20. When receiving this signal, theinformation addition unit 19 superimposes the copy inhibition videosuperimposition indication signal 18 indicating that the copy inhibitionvideo 17 is superimposed, upon the vertical blanking interval or thehorizontal blanking interval of the luminance signal or one or both ofthe color-difference signals, and the copy inhibition video insertionunit 20 carried out a process for inserting the copy inhibition video 17in the luminance signal and the color-difference signal as describedabove.

As described above, according to the copy protection method and thedigital broadcast receiver of the sixth embodiment, the copy inhibitionvideo 17 is superimposed upon a start part or an end part of a videoeffective period of a field, or a start part or an end part of a videoeffective period of a line of the luminance signal, and further the copyinhibition video superimposition indication signal 18 indicating thatthe copy inhibition video 17 is superimposed is superimposed upon thevertical blanking interval of the luminance signal. Therefore, at thenormal screen display, the copy inhibition video superimpositionindication signal 18 is detected, then the copy inhibition video 17 isdeleted from the luminance signal to restore this signal to the normalvideo signal, and the normal video signal is outputted, whereby thescreen display can be performed without being recognized by the viewersat all that the copy inhibition information is superimposed thereupon.On the other hand, when copied video is reproduced and displayed, thevideo is recorded without deleting the copy inhibition video 17 from theluminance signal and, when the copied video is displayed on TV or thelike, the copy inhibition video 17 is displayed in any of upper andlower parts and right and left parts of the display screen, whereby itcan be judged to be copied video.

INDUSTRIAL AVAILABILITY

The copy protection method and the digital broadcast receiver accordingto the present invention are greatly useful in carrying out the optimumcopy protection process for a component video signal which is composedof a luminance signal and two color-difference signals.

1. A copy protection method for a component video signal which iscomposed of a luminance signal and two color-difference signals,comprising steps of: on a digital broadcast receiver side, superimposingcopy inhibition information upon a first one of the two color-differencesignals and superimposing, upon a second one of the color-differencesignals, a copy inhibition information superimposition indication signalindicating that the copy inhibition information is superimposed upon thefirst color-difference signal; and on a recorder side, when the copyinhibition information superimposition indication signal is detected inthe second color-difference signal, analyzing the first color-differencesignal and, when the copy inhibition information is detected in thefirst color-difference signal, carrying out a copy inhibition processwithout performing recording.
 2. A digital broadcast receivercomprising: a copy guard detection unit for detecting whether inputvideo data is copy inhibited or not; and an information addition unitfor superimposing copy inhibition information upon a first one of twocolor-difference signals when the copy guard detection unit detects thatthe input video data is copy inhibited and superimposing, upon a secondone of the color-difference signals, a copy inhibition informationsuperimposition indication signal indicating that the copy inhibitioninformation is superimposed upon the first color-difference signal. 3.The copy protection method of claim 1 wherein the copy inhibitioninformation is superimposed upon the first color-difference signal andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal in field units orin line units.
 4. The digital broadcast receiver of claim 2 wherein whenthe copy inhibition information is superimposed upon the firstcolor-difference signal and the copy inhibition informationsuperimposition indication signal is superimposed upon the secondcolor-difference signal, the information addition unit performs thesuperimposition in field units or in line units.
 5. The copy protectionmethod of claim 1 wherein after the copy inhibition information issuperimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal, in field units, thesuperimposed color-difference signal of each field and acolor-difference signal of an immediately preceding field are composed.6. The digital broadcast receiver of claim 2 comprising: acolor-difference signal composition unit for, after the copy inhibitioninformation is superimposed upon the first color-difference signal andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal, in field units,composing the superimposed color-difference signal of a field and acolor-difference signal of an immediately preceding field.
 7. The copyprotection method of claim 1 wherein after the copy inhibitioninformation is superimposed upon the first color-difference signal andthe copy inhibition information superimposition indication signal issuperimposed upon the second color-difference signal, in line units, thesuperimposed color-difference signal of each line and a color-differencesignal of an immediately preceding line are composed.
 8. The digitalbroadcast receiver of claim 2 comprising: a color-difference signalcomposition unit for, after the copy inhibition information issuperimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal, in line units, composing thesuperimposed color-difference signal of a line and a color-differencesignal of an immediately preceding line.
 9. The copy protection methodof claim 1 wherein when the copy inhibition information is superimposedupon the first color-difference signal and the copy inhibitioninformation superimposition indication signal is superimposed upon thesecond color-difference signal, they are superimposed at irregularintervals.
 10. The digital broadcast receiver of claim 2 comprising: anadditional signal control unit for, when the copy inhibition informationis superimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal, performing control forsuperimposing the same at irregular intervals.
 11. The copy protectionmethod of claim 3 wherein when the copy inhibition information issuperimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal, they are superimposed atirregular intervals.
 12. The copy protection method of claim 5 whereinwhen the copy inhibition information is superimposed upon the firstcolor-difference signal and the copy inhibition informationsuperimposition indication signal is superimposed upon the secondcolor-difference signal, they are superimposed at irregular intervals.13. The copy protection method of claim 7 wherein when the copyinhibition information is superimposed upon the first color-differencesignal and the copy inhibition information superimposition indicationsignal is superimposed upon the second color-difference signal, they aresuperimposed at irregular intervals.
 14. The digital broadcast receiverof claim 4 comprising; an additional signal control unit for, when thecopy inhibition information is superimposed upon the firstcolor-difference signal and the copy inhibition informationsuperimposition indication signal is superimposed upon the secondcolor-difference signal, performing control for superimposing the sameat irregular intervals.
 15. The digital broadcast receiver of claim 6comprising: an additional signal control unit for, when the copyinhibition information is superimposed upon the first color-differencesignal and the copy inhibition information superimposition indicationsignal is superimposed upon the second color-difference signal,performing control for superimposing the same at irregular intervals.16. The digital broadcast receiver of claim 8 comprising: an additionalsignal control unit for, when the copy inhibition information issuperimposed upon the first color-difference signal and the copyinhibition information superimposition indication signal is superimposedupon the second color-difference signal, performing control forsuperimposing the same at irregular intervals.